1. Field of the Invention
The present invention relates to a photoresist composition and, more particularly, to a positive photoresist composition that comprises a polymer comprising a first repeating unit derived from a sulfonamide monomer including a fluorosulfonamide functionality.
2. Description of the Related Art
In the manufacture of semiconductors, the photolithographic process typically projects an ultraviolet (UV) light onto a semiconductor substrate coated with a layer of a photosensitive resist, i.e., a photoresist, through a mask that defines a particular pattern of electronic circuitry. Exposure to UV light, followed by baking, induces a photochemical reaction, which changes the solubility of the exposed regions of the photoresist. Thereafter, an appropriate developer, typically an aqueous base solution, is used to selectively remove the photoresist in the exposed regions or alternatively, in the unexposed regions, to create a patterned imaging layer. A photoresist that is removed from the exposed regions is called a positive photoresist, while a photoresist that is removed from the unexposed regions is called a negative photoresist. The patterned imaging layer typically overlies the semiconductor substrate, which may now be processed by another semiconductor manufacturing process, for example, etching or ion implantation, to create patterned processing of the now revealed semiconductor substrate.
Photoresists are generally comprised of a polymeric matrix, a radiation sensitive component, a casting solvent, and other performance enhancing additives. The polymeric matrix should have a reasonable absorption at exposure wavelengths. Another parameter to be considered in new photoresist materials is the dissolution behavior of the material in a given developer. The semiconductor industry has largely supported the use of 0.263 N tetramethyl ammonium hydroxide (TMAH) as a developer for photoresists.
In order to achieve the desired photolithographic performance, a positive photoresist should not swell upon contact with a developer and ideally, should show but slight dissolution (0-1 nm/s) in the developer before irradiation. After irradiation, positive photoresists in exposed regions should have a high dissolution rate in the developer, so that they can be easily removed and so subsequent processing is limited to the desired pattern.
To achieve the desired dissolution properties in an aqueous base developer, acidic groups are incorporated into the polymer structure. In photoresists exposed to light of a 248 nm wavelength, hydroxystyrene has been widely used as an acidic group. Hydroxystyrene, however, strongly absorbs light of a 193 nm wavelength, which is currently used in irradiating processes, and it is anticipated that irradiation processes will use even shorter wavelengths in the near future in order to enhance resolution. Instead, when using light of a 193 nm wavelength for exposure, acidic groups such as carboxylic acid (—COOH) and hexafluoroalcohol (HFA) are currently used. However, COOH is a relatively strong acidic group and has a strong affinity for a base developer. Polymers with COOH tend to swell and/or quickly dissolve in an aqueous base developer. Thus, it is difficult to achieve slight dissolution in the developer before irradiation with polymers having COOH acidic groups. The HFA acidic group is much weaker than COOH. Thus, photoresists based on HFA tend to have better dissolution properties. However, due to the high fluorine content in the HFA group, the etch resistance is often a concern.
Thus, there remains a need for a positive photoresist composition that exhibits an excellent dissolution response in an aqueous base developer, and yet overcomes the above-mentioned problems associated with photoresist compositions.